Figure 5. Ammonium Toxicity Induces Amino Acid Excretion.

LC-MS/MS was used to analyze filtrates from steady-state chemostats. The detected amino acids were expressed in nmoles based on standards (Materials and Methods). The detected amino acids were scaled for number of excreted nitrogen molecules per amino acid (i.e., one for alanine and two for glutamine) and expressed in nmoles excreted nitrogen per million cells.

(A) Excreted amino acids for a range of potassium (same as the chemostats shown in Figure 1).

(B) Excreted amino acids were measured for a range of ammonium in 1.3 mM potassium (same as the chemostats shown in Figure 3).